In plasma enhanced chemical vapor deposition (PECVD) and other similar processes, process gases may be introduced into the process chamber and ignited into a plasma by an RF current applied to the process chamber. Many PECVD processes include a gas delivery line to provide one or more process gases for forming a plasma and processing substrates with the plasma of the delivered gases. As substrate sizes increase, the RF current applied to the process chamber may also increase. With the increase in RF current, the possibility of premature gas breakdown prior to the gas reaching the process chamber also undesirably increases, as does the possibility of parasitic plasma formation inside the gas delivery line. Current PECVD systems include devices such as RF chokes to reduce premature gas breakdown and parasitic plasma formation. However, the inventors have observed that the RF chokes used in current PECVD systems are not always reliable, for example, to prevent premature gas breakdown prior to the gas reaching the process chamber and ensure the absence of parasitic plasma formation inside the gas delivery line.
Therefore, the inventors have provided an improved plasma process gas delivery apparatus.